1. Field of the Invention
The invention generally relates to systems for burning natural gas such as are particularly used for heating residential structures. The invention particularly relates to apparatus for metering a mixture of fuel and air which is supplied to a burner of such a system, the apparatus also serving as the sole sealing structure necessary between a chamber in which the fuel and air are mixed and the atmosphere.
2. Description of the Prior Art
Compact heat exchange systems are known which economically extract heat from the products of combustion formed on burning of a mixture of fuel and air. Such systems typically comprise a burner positioned inside a plenum formed by a heat exchanger having heat exchange surfaces which contact the products of combustion. Such heat exchange systems are described in U.S. Pat. Nos. 3,967,590, issued July 6, 1976, and 3,997,109, issued Dec. 14, 1976. These highly efficient heating systems are adapted to residential housing needs and must be susceptible to easy and inexpensive servicing not only when repair is necessary but also when it is desired to alter the heating capacity of the system or to convert the system to operation with an alternate fuel. When such an alteration or conversion is to be made, such as to the system described in U.S. Pat. No. 3,967,590, it has been necessary to employ the services of trained service personel sice adjustments requiring exact training were required. Accordingly, a need is seen in the art to simplify the alteration of heat capacity or conversion to alternate fuels, thereby to facilitate servicing of presently available heating systems.
Riot, in U.S. Pat. No. 3,371,699, provides an industrial gas burner having a plate-like structural member which allows proportional mixing of fuel and air, the device so disclosed being intended to allow constant attention in an industrial process to the quantities of fuel and air which are ducted to a burner. However, the gas mixing structure disclosed by Riot serves only to meter gases into a mixing chamber and does not provide any sealing function within the gas ducting portion of the system. In the Riot structure, structure additional to the plate-like member is required to seal the system. Accordingly, the prior art does not provide a simple, easily serviced gas metering structure which can be readily replaced without the need to remove and replace sealing structure associated with the gas metering structure. The prior art gas metering structures are relatively difficult and expensive to service when compared with the gas metering structure disclosed herein, the present gas metering structure allowing rapid field alteration of heating capacity and fuel conversion within a matter of minutes.